Utilize an AJAX call to fetch an array and incorporate it within your JavaScript code

Currently, I am in the process of building a live update chart feature. To access the necessary data, I created a separate file which contains the required information. Through AJAX, I sent a request from my main page to retrieve an Array and incorporate it into the main page. However, I encountered an issue where I cannot utilize this array outside of the request; rather, I can only use it within the <script> section. Below is what I have implemented:

<script>
    $(document).ready(function(){
      $.getJSON("loadchart.php", function(data){
          var sensor1 = data[0];
          var sensor2 = data[1];
          var sensor3 = data[2];
          var sensorsum = data[3];
      });
    });
    console.log(sensor1);

    //The code for my chart goes here

Upon attempting to log the array, an error message is displayed:

Uncaught ReferenceError: sensor1 is not defined
    at main.php:107

In an effort to resolve this issue, I came up with the following new approach:

async () => {
      async function foo() {
        return $.ajax({
          url: "loadchart.php",
          success: function(data){
            return data;
          }
        });
      }

    var result = await foo();

    console.log(result);
    };

Answer №1

There are a couple of reasons why sensor1 may be undefined.

Firstly, one reason could be that you declared the variable in a scope that is too low. If you try to access a variable outside of the callback function where it was declared, it won't be accessible.

Secondly, another reason could be that you are attempting to access the variable before it has been defined. In this case, the callback function that assigns a value to sensor1 gets executed only after a response is received from the API. So trying to access it immediately when the script runs will lead to an undefined value.

The solution would be:

$(document).ready(function(){
    $.getJSON("loadchart.php", function(data){
         var sensor1 = data[0];
         var sensor2 = data[1]; 
         var sensor3 = data[2]; 
         var sensorsum = data[3];

         //Move the console.log into this scope.
         console.log(sensor1);
     }); 
}); 

Remember, the console.log() will only display the value if:

The request to the API is successful

The returned data matches the expected structure.

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